1. Field of the Invention
This invention relates to aqueous liquid detergent compositions containing an oxidized polysaccharide component as a viscosity controlling agent.
2. Description of the Related Art
Heavy duty liquid detergents useful for machine washing of laundry are well known materials which have been described in a number of patents and in the literature. They are generally aqueous compositions comprising at least one or a compatible mixture of two or more detergent active surfactants selected from anionic, cationic, nonionic, zwitterionic and amphoteric species. Such compositions also generally contain detergency builder components and/or sequestering agents such as inorganic phosphates or phosphonates, alkali metal carbonates, alkali metal aminopolycarboxylates such as salts of nitrilotriacetic acid and salts of ethylenediamine-tetraacetic acid, alkali metal silicates, aluminosilicates, various zeolites and mixtures of two or more of these. Other components which may be present in such compositions include a clay material such as bentonite present as a fabric softener, optical brighteners, enzymes and their stabilizers, perfumes, colorants, antifoaming agents, e.g. silicone compounds, preservatives and like known additives.
One of the problems associated with such aqueous liquid detergent compositions is that they tend to be of initially high viscosity or tend to thicken after storage for a period of time thereby markedly decreasing the flowability of the compositions from the containers in which they are packaged. The flow problem is compounded with respect to compositions containing dispersed solid materials such as bentonite clay fabric softener and dispersed builders, and compounded even more where super concentrated detergent compositions containing less than about 50% by weight water are prepared.
The problem of viscosity control with respect to liquid detergent compositions has been addressed in a number of issued patents. For example, U.S. Pat. No. 4,715,969 and its counterpart UK 2,168,717 disclose that the addition of less than about 0.5% by weight of a polyacrylate polymer, e.g. sodium polyacrylate, having a molecular weight from about 1,000 to 5,000 to aqueous detergent compositions containing primarily anionic surfactants will stabilize the viscosity of the composition and prevent a major increase in viscosity after a period of storage of the formulated composition.
A disadvantage associated with the use of such polymeric viscosity stabilizers at relatively high levels is that they are not readily biodegradable after discharge into the environment.
PCT publication WO 91/09109 (EP 90/01962) addresses the problem of biodegradability of aqueous detergent compositions containing a dispersion of lamellar droplets of detergent active material and a polymeric suspending agent. The disclosure teaches the use of a biodegradable deflocculating polymer such as modified polysaccharide containing hydrophobic side chains as the suspending polymer, preferably a modified dextran polymer having a molecular weight in the range of from about 2,000 to 20,000.
In addition, Canadian patent 2,028,284 discloses powder detergent compositions containing a combination of phosphate salts and a zeolite material as sequestering agents, and further containing from about 5 to about 40% by weight of an oxidized polysaccharide, based on the weight of phosphate, zeolite and oxidized polysaccharide. The oxidized polysaccharide is disclosed to be biodegradable and to have sequestering (co-builder) properties which compliment the builder properties of the phosphates and zeolites, thereby allowing a reduction of the content of these latter materials in the laundry composition. A similar disclosure if found in Canadian patent 2,038,460.
There still exists a need in liquid detergent technology to provide aqueous formulations which contain a higher level of payload, i.e., active ingredients, while at the same time minimizing viscosity or viscosity build up associated with such highly concentrated formulations. This need is particularly acute with respect to phosphorus-free compositions containing non-water soluble detergent builders and clay softeners.